Vacuum-type circuit breaker comprising series-connected vacuum interrupters within a grounded tank

ABSTRACT

A high-voltage vacuum-type circuit breaker comprises a tubular grounded tank and a plurality of series-connected vacuum interrupters located within the tank. The interrupters are mounted in such positions that: (1) the longitudinal axes of the interrupter casings extend transversely of the central longitudinal axis of the tubular tank and (2) the movable contact rods of the interrupters project outwardly through the interrupter envelopes toward a single side of the tank. For operating the interrupters, there is provided a linkage extending between the interrupters adjacent the ends of the envelopes through which the movable contact rods extend.

United States Patent [191 Badey et al.

[52] US. Cl 200/144 B, 200/145 R [51] Int. Cl. H0lh 33/66 [58] Field of Search 200/144 B, 145, 148 B References Cited UNITED STATES PATENTS Oct. 1, 1974 Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-J.' Wesley Haubner; William Freedman 5 7 ABSTRACT A high-voltage vacuum-type circuit breaker comprises a tubular grounded tank and a plurality of seriesconnected vacuum interrupters located within the tank. The interrupters are mounted in such positions that: (l) the longitudinal axes of the interrupter casings extend transversely of the central longitudinal axis of the tubular tank and (2) the movable contact rods of the interrupters project outwardly through the interrupter envelopes toward a single side of the tank. For operating the interrupters, there is provided a linkage extending between the interrupters adjacent the ends of the envelopes through which the movable 3,052,783 9/1962 Buron ZOO/148 B Leeds B ontact rods extend 3,300,609 H1967 Flurscheim ct al ZOO/144B 3,350,528 10/1967 McKeough 200/145 R 9 Clalms, 3 Drawing Figures BACKGROUND This invention relates to a high voltage vacuum-type circuit breaker that comprises a grounded tank and a plurality of vacuum-type circuit interrupters located within the tank and electrically connected in series with each other.

Vacuum circuit breakers of this character have been proposed heretofore which comprise a tank of'cylindrical form and a series of vacuum interrupters arranged in aligned, end-to-end relationship along an axis that runs generally parallel to the longitudinal axis of the cylindrical tank. See, for example, US. Pat. No. 3,300,609-Flurscheim et al., especially FIGS. 7 and 13. One disadvantage of such an arrangement is that, in a high voltage circuit breaker, the interrupter assembly comprising the aligned interrupters becomes unduly long. Not only does this require a cylindrical tank of objectionably great length, but it' also complicates the problem of operating the interrupters in a precisely coordinated manner. A mechanicallinkag'e interconnecting the interrupters is likely to have so much yield in it because of its great length that the desired coordination in the operation of the interrupters cannot be consistently obtained.

Another disadvantage of the alig'ned interrupter arrangement referred to hereinabove is that an unduly large amount of capacitance is present between'the interrupters and the grounded tank. The presence of this large interrupter-to-ground capacitance makes it difficult to obtain a good voltage distribution between the interrupters when they are open. To be effective, the

usual capacitors connected across the interrupters for voltage-distribution purposes must be unduly large if the capacitance to ground islarge.

SUMMARY Accordingly, an object of our invention is to construct a vacuum circuit breaker of the type comprising a grounded cylindrical tank and series-connected vacuum interrupters located therein in such a manner that the interrupters: (1) can be accommodated in a tank of relatively short length and (2) canbem'echanically interconnected with an operating linkage of relatively short length.

Another object is to construct the circuit breaker in such a manner that the capacitance between the interrupters and the grounded tank is kept relatively low so as to facilitate obtaining the desired distribution of voltage between the interrupters.

In carrying out the invention in one form, we provide a tubular grounded tank and a plurality of seriesconnected vacuum interrupters located within the tank. The interrupters are mounted in such positions that: l the longitudinal axes of the interrupter casings extend transversely of the central longitudinal axis of the tubular tank and (2) the movable contact rods of the interrupters project outwardly through their associated interrupter envelopes toward a wall portion of the tank located at a single side of the central longitudinal axis of the tubular tank. For operating the interrupters, there is provided a linkage extending between the interrupters adjacent the ends of the envelopes through which the movable contact rods extend and means for coupling the linkage to said movable contact rods. The features designated (1) and (2) above contribute to attainment of the above-described objects of our invention.

BRIEF DESCRIPTION OF DRAWINGS For a better understanding of the invention, reference may be had to the following description taken in connection with the accompanying drawings, wherein:

FIG. 1 is a side elevational view, partly in section and partly schematic, showing a vacuum circuit breaker embodying one form of the invention.

FIG. 2 is a sectional view of one of the vacuum inter rupters utilized in the circuit breaker of FIG. 1.

FIG. 3 is a sectional view of a portion of a modified form of vacuum circuit breaker.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, the circuit breaker shown therein comprises a metal tank 12 at ground potential and a plurality of vacuum interrupters 14 located within the tank. The illustrated tank 12 comprises an elongated cylindrical portion 15 having a central longitudinal axis 16 that extends horizontally. At opposite ends of cylindrical'portion 15 are two dished heads 18 suitably secured to the cylindrical portion, as by bolted flange connections 20. Although we prefer that the tank be entirely or predominantly of metal, it can instead be of a suitable insulating material internally coated with metal at ground potential.

Adjacent the opposite ends of cylindrical tank portion 1 5, there are two tubular bushing pockets 22 extending transversely of the axis 16 and communicating with the interior of the tank. Disposed within each of these pockets 22 is a high voltage terminal bushing 28 of a conventional construction. Each of these terminal bushings comprises a rigid central conductor 30 and a housing 31 surrounding the conductor comprising two tubular shells 32 and 34 of procelain and a tubular midsection 35 of metal disposed between the porcelain shells. The parts of the bushing housing 31 are held together in compression by suitable clamping means comprising a stud 36 having a nut 37 threaded on its lower end and bearing against an end cap 38. It will be noted that the terminal bushings extend transversely of the longitudinal axis 16 of the cylindrical tank portion 15.

Referring to FIG. 2, each of the vacuum interrupters 14 is of a conventional design. As such, it comprises a highly-evacuated envelope 40 and a pair of separable contacts 42 and 43 within the envelope. The envelope comprises a tubular casing 45 of insulating material having a central longitudinal axis 56 and metal end caps 46 and 47 suitably sealed to the casing at its opposite ends. Contact 42 is a stationary contact fixed to the lower end of a stationary contact rod 49 that extends in sealed relationship through the upper end cap 46. Contact 43 is a movable contact fixed to the upper end of a movable contact rod 50 that extends freely through the lower end cap 47. A flexible metallic bellows 52 joined at its respective opposite ends to the movable contact rod 50 and end cap 47 provides a seal about the movable contact rod and allows for reciprocation of the contact rod without impairing the vacuum inside the envelope.

When the contacts 42 and 43 are in their engaged position, the vacuum interrupter is closed. Opening is effected by driving the movable contact rod 50 downwardly to separate the contacts. This establishes an are which is extinguished in a known manner at an early current zero. For condensing the arcing products, a tubular metal shield 55 surrounding the contacts in spaced relationship is provided within the envelope. This shield 55 is preferably electrically isolated from both contacts when the interrupter is open.

Closing of the interrupter is effected by driving the movable contact rod 50 upwardly from its open position to reengage the contacts 42 and 43. It will be noted that the movable contact rod 50 is movable during opening and closing along a path that is generally parallel to the central longitudinal axis 56 of the casing 45 of the vacuum interrupter.

For supporting the vacuum interrupters, we provide a plurality of hollow metal supports 60, on each of which a pair of the interrupters 14 is mounted, as shown in FIG. 1. In the illustrated embodiment, the metal support 60 for each pair of interrupters is located at the lower end of the interrupters. The movable contact end of each interrupter is shown fixed to its associated support 60, and the movable contact rod 50 projects into the interior of this hollow support 60. Although preferably entirely or predominantly of metal, each support 60 may be of insulating material suitably coated with metal.

The metal supports 60 are arranged in horizontallyspaced relationship and are fixed to each other by means of insulating tubes 64 disposed between the metal supports. These insulating tubes are suitably attached at their opposite ends to the supports 60. The metal supports 60, the insulating tubes 64 secured therebetween, and the interrupters 40 secured to supports 60 together form a unitary interrupting assembly. This unitary interrupting assembly is supported from the lower ends of the terminal bushings 28.

For supporting the interrupter assembly from the lower ends of the terminal bushings, two insulators 70 are provided at opposite ends of the interrupter assembly. Each insulator has end fixtures 72 and 74 fixed 'to its opposite ends. The upper end fixture 72 is suitably secured to the lower end of the terminal bushing, and the lower end fixture 74 is suitably secured to an end one of the metal housings 60. Additional support and rigidity can be provided for the interrupting assembly, if desired, by providing one or more additional insulating supports between the interrupting assembly and the tank 12 at spaced points along the length of the interrupting assembly.

In the embodiment shown in FIG. 1, an additional insulating support for the interrupter assembly is provided in the form of a tube 76 of insulating material extending horizontally between the interrupter assembly and the tank 12. This tube 76 is suitably attached at its opposite ends to the interrupter assembly and tank and forms a housing for the operating rod 80,soon to be described.

For operating the interrupters 14 substantially in unison, we provide an operating rod 80 that in FIG. 1 extends in a horizontal direction through the housings 60 and the insulating tubes 64. A portion of the operating rod 80 also extends between the housing 60 at the extreme right hand end of the interrupter assembly and a closing mechanism 82 for the interrupters located externally of the tank 12. The closing mechanism 82 may be of a conventional construction and is therefore shown in block form only. A suitable seal, preferably in the form of a bellows 83, is provided about the operating rod where it extends through the tank wall.

For coupling the operating rod to the movable contact rods 50 of the interrupters, a plurality of bellcranks 85, one for each interrupter, are provided. Two of these bellcranks are located within each of the metal housings 60 and are respectively mounted on stationary pivots 86. One arm of each bellcrank is pivotally connected at 87 to the operating rod 80, and the other arm is coupled through a suitable wipe device 90 to the movable contact rod 50 of its associated interrupter. The wipe device 90 is of a conventional design and is therefore not shown in detail. An example of a suitable wipe device is shown in FIGS. 1 and 2 of U.S. Pat. No. 3,180,960-Barkan et al., assigned to the assignee of the present invention.

The operating rod 80 preferably comprises a plurality of sections of insulating material and a plurality of sections of metal mechanically connected together in se ries. The section extending between the end housing 60 and the tank wall is of insulating material; the section within each of the housings 60 that interconnects the cranks 85 disposed therein is of metal; and the section extending between each adjacent pair of housings 60 through an insulating tube 64 is of insulating material.

When the operating rod 80 is driven to the right from its position of FIG. 1, each of the bellcranks 85 is pivoted in a counterclockwise direction about its stationary pivot 86, thus driving the associated movable contact rod 50 upwardly through a closing stroke. This causes the movable contact 43 of each interrupter to engage its associated stationary contact 42, thereby closing the interrupter. Opening of the circuit breaker is effected by driving the operating rod 80 to the left from its closed position. The power for driving the operating rod 80 to the left is derived from opening springs (not shown) inside the tank 12. These opening springs are charged by a closing operation and are held in their charged condition by a suitable latch (not shown), which is released to initiate opening.

The interrupters are electrically connected in series circuit relationship with each other and with the bushing conductors 30. For electrically connecting the interrupter assembly to the bushing conductors, a flexible connection is provided between the lower end of each bushing conductor and the upper end of the stationary contact rod 49 of the immediately-adjacent interrupter at the end of the assembly. Between the movable contact rods of the interrupters of each associated pair of interrupters, a flexible conductor 96 is connected. Between the stationary contact rods of the adjacent interrupters in adjacent pairs of interrupters, a conductor 97 is suitably connected. Thus, the current path through the interrupter assembly, when closed, is of a zig zag configuration; extending from conductor 95 downwardly through the first interrupter 14, then through conductor 96 and upwardly through the next interrupter 14, then through the conductor 97 and downwardly through the next interrupter, and so on.

When the circuit breaker is energized and closed. the interrupter assembly. including the housing 60, is at a high voltage with respect to the grounded metal tank 12. For electrically isolating the high voltage interrupter assembly from the grounded tank, a high dielectric strength insulating medium, preferably a gaseous insulator under pressure, is provided within the tank 12. A suitable gaseous insulator is sulphur hexafluoride at a pressure of about 50 to 75 p.s.i. gauge. in one form of circuit breaker, the interior of the bushings 28 is also filled with this gaseous insulator. Suitable openings (not shown) in the bushing housing afford communication between the interior of the bushings and the interior of the tank. As is well known, the presence of a high dielectric strength insulating medium in the tank and the bushings permits the electrical clearances and creepage distances therein to be very substantially reduced, as compated to what is required in air at atmospheric pressure. It is to be noted that the interiors of the housing 60 and the insulating tubes 64 and 76 are in free communication with the rest of the tank space and thus contain pressurized gaseous insulator. The presence of the gaseous insulator inside and outside insulating tubes 64 and 76 permits these tubes to be relatively short despite the high voltages to which they are subjected when the circuit breaker is open.

For reducing the likelihood of a dielectric breakdown between the high potential interrupting assembly and the grounded tank 12, we provide suitable electrostatic shielding (not shown) around the sharp edges of the conductive parts of the interrupting assembly. Such shielding is preferably provided about the conductors 97 and the projecting ends of the stationary contact rods and also in the form of covers (not shown) free of sharp edges for the openings in the bottom of housings 60. These covers and the housing 76 complete an enclosure around the moving parts of the interrupter assembly that helps to retain therein loose particles which might rub or flake off and prevent such particles from weakening the gaseous dielectric within the tank.

When the circuit breaker is open, the voltage that is present thereacross is distributed substantially equally between the interrupters by means of voltage-dividing capacitors 100 connected across the individual interrupters. Each of these capacitors 100 is preferably a ceramic capacitor stack of the type shown and claimed in US. Pat. No. 3,586,934-Nakata, assigned to the assignee of the present invention. Two of these capacitors are preferably connected in series between the upper contact rods of each associated pair of interrupters. Between these two capacitors, a conductive strap 102 is provided that is connected at its lower end to the metal housing 60 on which the two interrupters are mounted and at its upper end to the junction between the two capacitors 100.

It will be noted that the interrupters are mounted in such positions that the central longitudinal axis of the insulating casing 45 of each interrupter extends transversely of the central longitudinal axis 16 of the tubular metal tank 12. This disposition of the interrupters not only enables us to utilize a tank of relatively short length for enclosing the interrupters with the required electrical clearances but also enables us to employ a relatively short operating rod 80 for actuating the interrupters. In our circuit breaker, the portion of the operating rod that interconnects the interrupters is required to extend only along the transverse dimension of the interrupters and no substantial added length is needed to accommodate the rod-to-interrupter linkage portions 85. Where the interrupters are in aligned end-toend relationship as in the aforesaid Flurscheim et al. US. Pat. No. 3,300,609, the operating rod must extend along the entire length of the interrupters and of the spaces therebetween needed to accommodate the rodto-interrupter linkage portions; and this necessitates a considerably longer operating rod. This much longer operating rod is susceptible to a considerably greater amount of yield, and this makes it more difficult to precisely coordinate the operation of the interrupters.

Another important advantage of positioning the interrupters with the longitudinal axes of their casings extending transversely of the longitudinal axis 16 of the tubular tank 12 is that the capacitance between the interrupters and ground is considerably reduced. This capacitance is a direct function of the area of the high voltage electrode structure that faces the grounded tank. Where the interrupters are arranged with their longitudinal axes parallel to the tank axis 16, a much larger high-voltage electrode area faces the cylindrical tank that is the case with the disclosed arrangement. By materially reducing this area, we materially reduce the interrupter-to-ground capacitance. An advantage of reducing this interrupter-to-ground capacitance is that much smaller capacitors 100 connected across the interrupters can be used for properly distributing the voltage between the interrupters. For a discussion of how capacitance to ground affects voltage distribution, reference may be had to US. Pat. No. 2,840,670-Leeds et al.

It will be further noted that in FIG. 1 the movable contact rods of the interrupters 14 all project outwardly through their associated envelopes 40 in a downward direction, or stated more generally, toward a wall portion of the tank 12 that is located at a single side (the lower side in FIG. 1) of the central longitudinal axis 16 of the tubular tank 12. This feature, combined with the fact that the lower ends of the movable contact rods 50 are disposed closely adjacent the operating rod 80, enables the interrupters to be operated with a simple linkage 80, 85 and also enables the metal housings to be disposed in substantially aligned relationship and to be interconnected by simple insulating tubes 64. In the preferred form of our invention shown in FIG. 1, the lower ends of the contact rods 50, when viewed in a horizontal direction from the end of tubular tank 12, are disposed in substantially aligned relationship.

Another advantage of positioning the interrupters so that the movable contact rods 50 of each pair of interrupters on a given support housing 11 are adjacent each other is that a very close, or stiff, coupling can readily be provided between the movable contact rods of the pair. This stiff coupling is made possibly by the physical closeness of the two contact rods 50 and also by the fact that these two contact rods (being at the same electrical potential) can be, and are, coupled together by a metal section of the operating rod 80. Generally speaking, the metal sections of an operating rod are stiffer than insulating sections of corresponding length. This stiff coupling between the interrupters of a given pair facilitates closing these two interrupters essentially simultaneously, i.e., causing their contacts to engage at substantially the same instant, which desirably limits the duration of any prestrikes on closing.

Preferably, the two interrupters mounted on each support housing 60 are disposed so that their longitudinal axes diverge relative to, each other. This provides a greater electrical clearance distance between the upper ends of the two interrupters, as compared to two interrupters spaced apart by a corresponding distance at their lower ends and having their longitudinal axes parallel. This greater electrical clearance distance is desirable because the upper ends of the interrupters are at widely different potentials relative to each other when the circuit breaker is open and energized. Considered in another way, for a given clearance distance between the upper ends of the interrupters, the lower ends of the divergently-mounted interrupters will be closer together, thus requiring less space for supports 60, thus contributing to the compactness of the circuit breaker and shortening the length of operating rod 80.

Another advantage of the above-described divergence of the axes of a pair of interrupters is that it results in the movable contact rods of the pair being closer together, thus making possible a closer, or stiffer, mechanical coupling between the two contact rods.

While we have shown a circuit breaker in which a single operating rod connected to an operating mechanism at one end of the interrupter assembly is utilized for operating the interrupters 14, our invention in its broader aspects has application to other types of circuit breakers. For example, it is applicable to the type shown in FIG. 3 where the operating rod (80) extends transversely of the interrupter assembly to a point near its center and there connects to linkages 80a and 80b for respectively operating the groups of interrupters at opposite sides of the operating rod connection shown at 81. The operating rod connection 81 is of a conventional form which operates linkages 80a and80bin opposite directions in response to actuation of the operating rod. The positioning of the interrupters 14 in FIG. 3 with their longitudinal axes disposed transversely of the longitudinal axis of tank 12 enables each of the operating linkages 80a and 80b to be shortened in the same manner as described hereinabove in connection with FIG. 1.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters patent of the United States is:

l. A vacuum-type circuit breaker comprising:

a. a tubular tank at substantially ground potential having a central longitudinal axis,

b. a plurality of vacuum interrupters located within said tank and electrically connected in series,

0. each of said vacuum interrupters comprising a highlyevacuated envelope comprising a casing of tubular form at least partially of insulating material having a central longitudinal axis, separable contacts within said envelope, and contact rods for respectively supporting said contacts, one of said contact rods being movable generally parallel to the longitudinal axis of said casing and projecting through one end of said envelope, d. means for mounting said vacuum interrupters in such positions that: (i) the longitudinal axis of the casing of each of said interrupters extends transversely of the central longitudinal axis of the tubular tank of the circuit breaker and (ii) the movable contact rods of said interrupters project through the interrupter envelopes from the interior of the envelopes toward a wall portion of said tank lo cated at a single side of the central longitudinal axis of the tubular tank,

e. and means for operating said interrupters comprising: (i) a linkage extending between said interrupters adjacent the ends of said envelopes through which said movable contact rods extend and (ii) means for coupling said linkage to said movable contact rods, said linkage comprising portions of insulating material located between the ends of said envelopes that are at different potentials when said circuit breaker is open and energized.

2. The vacuum-type circuit breaker of claim 1 in which the current path through said series-connected interrupters is of a zig-zag form.

3. The vacuum-type circuit breaker of claim 1 which further comprises: a pair of space-apart high voltage bushings respectivelylocated at opposite ends of said tubular tan and extending transversely of the central longitudinal axis of the tank, each bushing comprising a conductor for carrying current to and from said interrupters, and means for respectively electrically connecting the end ones of said interrupters to said bushing conductors.

4. The vacuum type circuit breaker of claim 1 in which said tank is filled with pressurized insulating gas.

5. The circuit breaker of claim 1 in which the mounting means for said interrupters comprises:

a. a linkage housing for each pair of interrupters on which the interrupters of said pair are mounted,

b. and means for mechanically interconnecting said linkage housings in spaced-apart substantially aligned relationship along an axis extending generally parallel to the central longitudinal axis of said tank.

6. The circuit breaker of claim 5 in which said means for mechanically interconnecting said linkage housings comprises tubes at least partially of insulating material respectively disposed between immediately-adjacent linkage housings.

7. The circuit breaker of claim 6 in which said insulating portions of said linkage extend through said tubes of insulating material.

8. The circuit breaker of claim 1 in which the mounting means for said interrupters comprises:

a. a linkage housing for each pair of interrupters, said linkage housings being disposed in spaced-apart relationship,

b. and means for mounting each pair of interrupters on its associated linkage housing in such positions that the central longitudinal axes of the casings of said pair extend in divergent relationship from said linkage housing.

9. The circuit breaker of claim 1 in which the ends of the movable contact rods of said interrupters are disposed in generally aligned relationship along an axis extending generally parallel to the central longitudinal axis of said tubular tank. 

1. A vacuum-type circuit breaker comprising: a. a tubular tank at substantially ground potential having a central longitudinal axis, b. a plurality of vacuum interrupters located within said tank and electrically connected in series, c. each of said vacuum interrupters comprising a highlyevacuated envelope comprising a casing of tubular form at least partially of insulating material having a central longitudinal axis, separable contacts within said envelope, and contact rods for respectively supporting said contacts, one of said contact rods being movable generally parallel to the longitudinal axis of said casing and projecting through one end of said envelope, d. means for mounting said vacuum interrupters in such positions that: (i) the longitudinal axis of the casing of each of said interrupters extends transversely of the central longitudinal axis of the tubular tank of the circuit breaker and (ii) the movable contact rods of said interrupters project through the interrupter envelopes from the interior of the envelopes toward a wall portion of said tank located at a single side of the central longitudinal axis of the tubular tank, e. and means for operating said interrupters comprising: (i) a linkage extending between said interrupters adjacent the ends of said envelopes through which said movable contact rods extend and (ii) means for coupling said linkage to said movable contact rods, said linkage comprising portions of insulating material located between the ends of said envelopes that are at different potentials when said circuit breaker is open and energized.
 2. The vacuum-type circuit breaker of claim 1 in which the current path through said series-connected interrupters is of a zig-zag form.
 3. The vacuum-type circuit breaker of claim 1 which further comprises: a pair of space-apart high voltage bushings respectively located at opposite ends of said tubular tan and extending transversely of the central longitudinal axis of the tank, each bushing comprising a conductor for carrying current to and from said interrupters, and means for respectively electrically connecting the end ones of said interrupters to said bushing conductors.
 4. The vacuum type circuit breaker of claim 1 in which said tank is filled with pressurized insulating gas.
 5. The circuit breaker of claim 1 in which the mounting means for said interrupters comprises: a. a linkage housing for each pair of interrupters on which the interrupters of said pair are mounted, b. and means for mechanically interconnecting said linkage housings in spaced-apart substantially aligned relationship along an axis extending generally parallel to the central longitudinal axis of said tank.
 6. The circuit breaker of claim 5 in which said means for mechanically interconnecting said linkage housings comprises tubes at least partially of insulating material respectively disposed between immediately-adjacent linkage housings.
 7. The circuit breaker of claim 6 in which said insulating portions of said linkage extend through said tubes of insulating material.
 8. The circuit breaker of claim 1 in which the mounting means for said interrupters comprises: a. a linkage housing for each pair of interrupters, said linkage housings being disposed in spaced-apart relationship, b. and means for mounting each pair of interrupters on its associated linkage housing in such positions that the central longitudinal axes of the casings of said pair extend in divergent relationship from said linkage housing.
 9. The circuit breaker of claim 1 in which the ends of the movable contact rods of said interrupters are disposed in generally aligned relationship along an axis extending generally parallel to the central longitudinal axis of said tubular tank. 